1. Field of the Invention
This invention relates to electro-optic devices, more particularly to beam steering devices.
2. Background of the Invention
Light may be steered by many classes of electro-optic devices. Among these are galvanometric scanners, resonant mirrors, and rotating polygon mirrors.
Galvanometric scanners reflect light off a mirror rotating about an axis through a small angle. The rotation results from application of an electrical current in the presence of a fixed magnetic field. The current generates a proportional magnetic field. The interaction between the two magnetic fields causes the lead conducting the current to twist. The twisting motion drives a mirror used to steer light.
Resonant mirrors reflect light off a mirror that also moves in response to an electrical signal. The signal drives a component, such as a voice coil, which presses against a spring-mounted, hinged mirror. A counterweight attached to the mirror and the mirror act together like a tuning fork. The mirror then oscillates at a resonant frequency to steer light.
A rotating polygon mirror normally consists of a multi-faceted mirror rotated at high speed by a motor. The mirror elements are typically facets cut onto the periphery of a disk, though other shapes exist. This assembly occurs more frequently in optical scanners, converting digital inputs to light patterns, than in other applications.
All three of these examples are relatively large, expensive and susceptible to shock and vibration. These disadvantages limit the applicability of these devices in a size-constrained and/or a mobile environment. A need has arisen for a means for steering light that is very compact, inexpensive, power efficient and usable in a mobile environment.